Device and method for feeding taped electrical components

ABSTRACT

A drive wheel ( 7 ) for the tape ( 1 ) accommodating the components ( 4 ) is provided with an angle measuring device ( 13, 14 ) which allows for a finely tuned rotational adjustment of the drive wheel ( 7 ). The pick-up position of the components ( 4 ) can be detected by means of a scanning optical system and can be corrected such that the pouch center can be set precisely to a constant advance position.

[0001] The invention relates to a device for feeding taped electricalcomponents in a feeding mechanism with a drive for the advancement of atape accommodating the components, whereby the components are taken upin pouches on the tape and can be transported stepwise to a definedpick-up position, whereby the drive comprises a motor and a drive wheeldriven by the motor, whereby the tape is provided with feed holes intowhich the transport pins of the drive wheel engage, and whereby thedrive is provided with a control facility for modifying the advancedistance.

[0002] Feed modules of this type are normally provided with a sprocketwheel whose radially projecting pins engage in feed holes in the tapeand which is rotated in defined angular steps in accordance with theseparation spacing of the pouches on the tape. The pouches have adefined positional relationship with respect to the feed holes. At theend of the manufacturing process, centering marks having a definedpositional relationship with respect to the pins on the sprocket wheeland which are intended to compensate for the production tolerances areapplied on the feed modules in the area of the pick-up point. Inaddition, it is usual after installing the feed module to measure theposition of the centering marks on the feed module in a feed zone of anautomatic component mounting machine by means of a camera located on atraveling component mounting head in order to be able to compensate forthe installation tolerances. In this situation, operational deviationsin the drive system of the feed module cannot be fully eliminated.

[0003] As modern technologies have developed, an ever greater level ofminiaturization has become a feature of the components to be mounted. Itis normal to provide the mounting head with a suction gripping devicewhich is placed over the components to be picked up and which attachesthese by suction to its front. In this situation, the gripping devicemust dip into the pouch in order to be able to come into contact withthe component. The permissible tolerances between the feed hole and thepouch are so great that the suction gripping device carrying out thepick-up operation cannot reliably be set up accurately for the componentto be picked up and comes into contact with the edge of the pouch andthereby fails to collect the component. In this situation, however, atleast over a fairly long section of the tape this is a case of asystematic fault.

[0004] The feed mechanisms are designed such that they can for examplebe operated in accordance with EP 0 589 275 A1 with different separationspacings, whereby a drive motor performs a different number of rotationsper advance step before the drive shaft is transported against arotation stop. Depending on the length of the components, the centralposition of the component pouch can vary in the pick-up position withina pick-up area. This deviation is taken into consideration by means ofan appropriate correction in the position of the mounting head.

[0005] According to WO98/37744 A1, for example, it is furthermore normalto arrange a positioning arm for guiding the mounting head in such a waythat it extends in the direction of the series of feed mechanisms whichare arranged side by side. When the different components are picked fromthe individual feed mechanisms, the positioning arm must then executecorresponding correction steps depending on the position of thecomponents to be picked up.

[0006] According to U.S. Pat. No. 6,032,845 A, a feed mechanism isfurthermore provided with a tape drive whose advance distance can beadjusted depending on the separation spacing of the components on thetape. This is driven by means of a transport wheel with radiallyprojecting pins which engage in the feed holes in the tape. An opticalsensor is directed onto the teeth and can thus monitor the precisefunctional setting of one of the teeth.

[0007] In addition, a modular feed mechanism has become known as aresult of EP 0345061 A, in which the component tape can be advanced bymeans of a slider with retractable transport pins. The length of strokeof the slider, which is driven by a compressed-air cylinder, and thusthe advance distance of the tape can be set manually by means of anadjustable stop to the relevant spacing division for the tape. Such achange of setting is necessary whenever a tape having a differentspacing division is mounted.

[0008] The object of the present invention is to facilitate the pick-upof the components in the event of a positional deviation.

[0009] This object is achieved by the invention according to claim 1.

[0010] As a result of the fine level of variability for the advancementlength, it is possible to perform an adjustment precisely to a specificpick-up position regardless of the size of the advancement and of itslongitudinal deviation on the tape. This adjustment step can be carriedout for example following every tape change by measuring the actualposition of the component or of the component pouch by using the cameraattached to the component mounting head. This operation can also beperformed between two tape change operations if the fault rate increasessignificantly during the pick-up operation particularly in the case ofvery small components. A particular advantage consists in the fact thatit is possible in this manner to align all the pick-up points for agroup of feed mechanisms in a single line such that the positioning armcan stand in a fixed position while the multiple mounting head istraveling to the different pick-up locations, which results in areduction in the corresponding drive and time resource requirements. Thefine level of variability of the advancement length also results in thefact that the central position of components having greatly differinglengths can always be set to the same pick-up position without anadditional preparatory resource requirement.

[0011] According to one advantageous development of the invention, thedrive has a drive wheel capable of being coupled to the tape, which isprovided with an angle measuring scale, and the feed mechanism isprovided with a corresponding sensing device. As a result of the directassignment of this encoder to the drive wheel, the position sensing iscarried out directly on the drive element. In this situation, motor andgearbox tolerances are totally excluded. The angle scale can for examplecomprise an optical or magnetic marking which is sensed using acorresponding sensor head.

[0012] According to another development of the invention, a large numberof the feed mechanisms are arranged side by side on a carrierperpendicular to the advance direction and the pick-up points for theindividual feed mechanisms can be aligned in a straight line. By thismeans it is possible to transport a mounting head over the pick-uppoints in a stationary longitudinal guide, such as is shown for examplein EP 0373373 B1 (FIGS. 5 to 7), without it being necessary in thissituation to adjust the position of the nozzle in the conveyor directionto the actual pick-up position.

[0013] According to a method for feeding the components in accordancewith claim 4, the position of the components in the pick-up position isdetermined by means of a measuring device and the pick-up position ofthe components is corrected by changing the stopping position of thedrive. By measuring the presented components or the associated tapepouch, positional deviations in the feed mechanism and also in the tapeitself can be detected and can be compensated for by correcting thestopping position.

[0014] The invention will be described in detail in the following withreference to an exemplary embodiment shown in the drawings. In thedrawings:

[0015]FIG. 1 shows a side view of a component mounting head and apartially revealed feed mechanism having a component tape; and

[0016]FIG. 2 shows a top view of the feed mechanism according to FIG. 1.

[0017] According to FIGS. 1 and 2, a conveyor-like tape 1 having lateralfeed holes 2 and pouches 3 for components 4 inserted therein is providedand inserted into a disk-like flat feed mechanism 5 which is fixed in adefined position in the traveling area of a mounting head 6 of acomponent mounting device. The feed mechanism 5 comprises a drive wheel7, which can be driven stepwise, having peripheral projecting transportpins 8 which engage without free play in the feed holes 2 in the tape 1.The positional relationship between the pouches and the feed holes isdefined by relevant standards. The additional tolerances in this caseare however almost as great as the lateral dimensions of the smallestcomponents.

[0018] On its underside facing the tape, the component mounting head hasa suction gripping device 9 and a scanning optical system 10 in the formof a CCT camera whose lens is surrounded by a lighting facility 11 whichilluminates the field of view of the scanning optical system 10. Thelighting facility 11 can comprise, for example, a large number oflight-emitting diodes having different wavelengths and differentorientations. In order to accommodate the different tape types, it ispossible to control a favorable selection of the diodes in such a waythat the structural features of the tape or of the components are shownup in high contrast and can be reliably detected.

[0019] The scanning optical system 10 is directed onto a pick-up point12 for the components in the feed mechanism 5. It is capable ofdetecting structural features 14, for example the edges of an emptypouch. It is connected to an image evaluation unit 13 which uses thisdata to calculate the central position of the pouch. The position of thepouch 3 with respect to the feed hole will change little over a fairlylong section of the tape. This means that the measured values can beused for correcting the pick-up over a fairly long sequence of pouches.In case the number of pick-up faults should increase, then the measuringoperation can be performed again in order to be able to determine thechanged pick-up position.

[0020] On its flat side the drive wheel is provided with a rotatingangular scale 13 in the form of a magnetized film. Directed at thelatter is a sensor head 14 in a stationary arrangement which is capableof detecting the angular position of the drive wheel and conveying it toa control facility 15. In the following drive step, this facilitycontrols a drive motor 16 in such a manner that the advance distance ismodified by the ascertained correction amount. A consistent separationspacing can then be maintained in the following feed steps.

1. Device for feeding taped electrical components (4) in a feedingmechanism (5) with a drive for the advancement of a tape (1)accommodating the components (4), whereby the components (4) are takenup in pouches on the tape (1) and can be transported stepwise to adefined pick-up position, whereby the drive comprises a motor (16) and adrive wheel (7) driven by the latter, whereby the tape (1) is providedwith feed holes (2) in which the transport pins (8) of the drive wheel(7) engage, and whereby the drive is provided with a control facilityfor modifying the advance distance, characterized in that the controlfacility comprises means for modifying the advance length with a finelevel of variability in order to achieve small correction steps. 2.Device according to claim 1, characterized in that the drive wheel (7)is provided with a finely graduated angle scale (13), and that the feedmechanism has a corresponding sensor head (14).
 3. Device according toclaim 1 or 2, characterized in that a large number of the feedmechanisms (5) are arranged side by side on a carrier perpendicular tothe advance direction and that the pick-up points (12) for theindividual feed mechanisms (5) can be aligned in a straight line. 4.Method for feeding taped electrical components (4) by means of a feedingmechanism (5) according to claim 1, 2 or 3, in a device for mountingcomponents (4) on substrates, whereby a tape (1) accommodating theelectrical components (4) is advanced stepwise by means of a drive forthe feed mechanism (5), and whereby structural features associated withthe pick-up points (12) for the components (4) can be sensed opticallyby means of a measuring device (10, for example) on the componentmounting device, characterized in that the measuring device is directeddirectly onto the pouches on the tape (1) and the precise pick-upposition of the components (4) is determined, and that the pick-upposition of the components (4) is corrected by changing the stoppingposition of the drive.